Quiz: Broken Math

Where you find that one plus one doesn’t always equal two.

Most Ruby operators are actually methods. For example, the + operator on integers is syntactic sugar for a method named Fixnum#+. When you write 1 + 1, the parser internally converts it to 1.+(1).

The cool thing about methods is that you can redefine them. So, here’s your challenge: break the rules of math by redefining Fixnum#+ so that it always returns the correct result plus one. For example:

​	1 + 1 ​# => 3​

Quiz Solution

You can solve this quiz with an Open Class (). Just reopen Fixnum and redefine + so that (x + y) becomes (x + y + 1). This is not as easy as it seems, however. The new version of + relies on the old version of +, so you need to wrap your old version with the new version. You can do that with an Around Alias ():

​	​class​ Fixnum
​	alias_method :old_plus, :+
​
​	​def​ +(value)
​	self.old_plus(value).old_plus(1)
​	​end​
​	​end​

Now you have the power to wreak havoc on Ruby’s basic arithmetic. Enjoy this code responsibly.

Отправить